SACAA ATPL Radio Aids Practice Questions - SACAA Airline Transport Pilot Licence (Aeroplane) Radio Aids Examination Exam

High solar radiation ionises the dense D-region, causing heavy collision-frequency absorption of lower HF frequencies The D-region vanishes entirely during daylight hours The D-region reflects HF signals back into space without ionospheric return Atmospheric humidity in the D-region absorbs HF signals during the day